Shigeo Minami - Academia.edu (original) (raw)

Papers by Shigeo Minami

Research paper thumbnail of Image amplification with local addressing by two-wave coupling in a Bi_12SiO_20 crystal by application of direct-current voltage

Journal of the Optical Society of America B, 1990

We present a proposal and an analysis of local image amplification by two-wave coupling in a Bi12... more We present a proposal and an analysis of local image amplification by two-wave coupling in a Bi12SiO20 crystal by applying external dc voltage. The analogy of two-wave coupling to an optical transistor array is discussed. It is found through the experiments that the local gain in amplification is given not by the reference-beam pattern alone but also by the electric field that is formed by the local photoconductance of the Bi12SiO20 crystal. A resistance-network model is used for analysis of the electric-field distribution. A variety of experiments verify the theoretical and calculated analyses. A sample reference pattern for amplifying segments of a signal image is designed through the resistance-network analysis of the electric-field distribution.

Research paper thumbnail of A Dual Wavelength Atomic Absorption Spectrophotometer Using a Pulsed Hollow Cathode Lamp

Applied Spectroscopy, 1977

A novel use of pulsed hollow cathode lamps for the purpose of background correction with a dual w... more A novel use of pulsed hollow cathode lamps for the purpose of background correction with a dual wavelength atomic absorption spectrophotometer is described. The pulsed hollow cathode lamp in conjunction with a transient signal gating system behaves as if the analyte source and the background correction source are firing alternately in time. Determinations of Fe, Mg, and Cd are carried out in order to evaluate the performance in practical analyses. Procedures and results on the time-resolved measurement of emission spectra and resonance line profiles from several kinds of pulsed hollow cathode lamps are also demonstrated in detail.

Research paper thumbnail of An Optical Null Double-Beam Double-Pass Infrared Spectrophotometer

Applied Optics, 1963

A novel signal treatment for an optical null double-beam double-pass system is developed and used... more A novel signal treatment for an optical null double-beam double-pass system is developed and used in a vacuum-type prism infrared spectrophotometer. A feature of this instrument is the arrangement of the specially-shaped beam switch and the second chopper working in conjunction with the phase-sensitive rectifier. The beam switch is made so that the lower half of the reference beam and the upper half of the sample beam are sent to the monochromator optics during one half of the cycle; the other parts of reference and sample beams reach the monochromator optics during the other half of the cycle. The second chopper alternately blocks the upper and lower halves of the image formed at the focal point of single-pass beam in proper synchronism with the beam switch. Fairly good cancellation of the scattered radiation was achieved through adjustment of the phase relation between the beam choppers and the phase-sensitive rectification system. In addition to reporting the general design and construction, detailed descriptions of the control and recording systems which provide the unique features are also included.

Research paper thumbnail of Three-dimensional phase contrast imaging by an annular illumination microscope

Applied Optics, 1990

A method of observing 3-D phase structures through a microscope incorporating computer reconstruc... more A method of observing 3-D phase structures through a microscope incorporating computer reconstruction is discussed. This microscope is equipped with an annular pupil in illumination optics, but no phase shifter is included in the imaging optics. The sample stage is longitudinally (z-axial) scanned to collect a focus image series. The 3-D phase transfer function is derived and computer-plotted based on Streibl's 3-D image transfer theory under the first-order Born approximation and the mutual intensity propagation theorem. Experimental results of 3-D phase reconstruction are shown with cultured tobacco cells by Helstrom's inverse filtering of the transfer function to a series of focused images.

Research paper thumbnail of Three-dimensional phase-contrast imaging by a computed-tomography microscope

Applied Optics, 1992

We report a technique for measuring the three-dimensional variation of refractive indices in a mi... more We report a technique for measuring the three-dimensional variation of refractive indices in a microscopic sample. The technique is an adaptation of optical computed tomography and is effective in measuring the three-dimensional refractive-index distribution of a nonabsorbing microscopic sample. Our report also includes a discussion of the conditions for the unambiguous application of the technique as well as results of experiments conducted with Aspergillus oryzae (commonly known as green mold) as the sample.

Research paper thumbnail of Application of Optical Multichannel Dectors to Spectroscopic Measurement

Journal of the Spectroscopical Society of Japan, 1991

Research paper thumbnail of Evaluation of Numerical Filters for Smoothing Spectroscopic Data

Japanese Journal of Applied Physics, 1969

In recent years, numerical filtering is often used for the smoothing of spectroscopic data. This ... more In recent years, numerical filtering is often used for the smoothing of spectroscopic data. This article is concerned with the computer analysis of numerical filters to find their optimal setup for spectroscopic measurements. Gaussian and Lorentzian contours are assumed for shapes of input signals to the filter in consideration of spectroscopic measurements. The distortion of the signal waveforms and the output noise levels are computed for the input data contaminated with the white or correlated noise. From the computed results which are summalized in the graphical presentation, optimal operating parameters of the data source and the succeeding filtering system are easily determined.

Research paper thumbnail of A Simple Photomultiplier Gating Circuit for the Nanosecond Region

Japanese Journal of Applied Physics, 1976

A novel nanosecond photomultiplier gating circuit is developed and applied to three kinds of phot... more A novel nanosecond photomultiplier gating circuit is developed and applied to three kinds of photomultiplier tubes. For the purpose of simply accomplishing accurate gating operation in the nanosecond region, even numbered dynodes which are deeply biased are simultaneously controlled by the delayed pulses which are adjusted in time so as to synchronize with traveling electrons in the tube. To evaluate

Research paper thumbnail of Corrected Performance of SIT Vidicons Exposed to Transient Radiation

Applied Spectroscopy, 1990

ABSTRACT The SIT vidicon detector has many features which would indicate utility as a detector fo... more ABSTRACT The SIT vidicon detector has many features which would indicate utility as a detector for time-resolved spectroscopy. Unfortunately, the problem of capacitive lag, under pulsed detection modes, can lead to highly erroneous spectroscopic intensities and linewidths. We have theoretically modeled the capacitive lag characteristics of the SIT vidicon and have developed a mathematical "correction factor" which can result in greatly enhanced performance. Results will be described for pulsed-LED test sources. Application to a variety of transient discharges appears possible.

Research paper thumbnail of A Nanosecond Photon-Counting Fluorimetric System Using a Modified Multichannel Vernier Chronotron

Applied Spectroscopy, 1985

A new time-resolved photon-counting instrument with high data-gathering efficiency is described. ... more A new time-resolved photon-counting instrument with high data-gathering efficiency is described. The principle of operation is based on the measurement of the nanosecond temporal distribution of the emitted photon burst during the short duration of transient emission. The instrument is characterized by the unique capabilities of a modified vernier chronotron with plural coincidence circuits and serial-timing data memories, which serve as an efficient multichannel event-time analyzer of 1.5-ns time resolution. The data-gathering efficiency is improved by a factor of 20 or more in comparison with that of the conventional single-photon counting method. In regular operation, the time history of transient emission for the period of 144 ns is obtained; and for phenomena with longer duration, the time-scale expansion mode of operation is provided. To demonstrate the whole system performance, a fluorescence decay curve of 1-ppm quinine sulfate in 0.1-N H2SO4 is presented.

Research paper thumbnail of A Pulse-Operated Microwave-Induced Plasma Source

Applied Spectroscopy, 1989

A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational dif... more A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational difficulties of the MIP due to Joule heating and to obtain spectral emission lines of high peak intensities, one energizes the MIP source with a TM010 cavity with a microwave pulse of large peak power and short duration, which is superposed on a low-bias dc microwave. A peak power of 400 W, which is two times the maximum output ratings of a magnetron under a normal dc operation, can be generated by applying a −500 V pulse to the cathode of the magnetron operating under the bias mode. The pulsed-MIP requires no special cooling system since the mean power remains low during the entire operation. Some of the considerations taken into account in the design and construction of the microwave generator are presented. The electrical and spectral characteristics of the MIP source are also described in detail.

Research paper thumbnail of A Small Laboratory Automation System Composed of Microcomputer-Based Spectrophotometers

Applied Spectroscopy, 1983

A distributed microcomputer network system which consists of integral microprocessors in intellig... more A distributed microcomputer network system which consists of integral microprocessors in intelligent instruments has been developed for automating the spectroscopy laboratory. In this system, the master-slave arrangement of microcomputers is adopted to compose the system controller and three microcomputer-based spectrophotometers (an UV/visible spectrophotometer, an IR spectrophotometer, and a fluorescence spectrophotometer). The IEEE-488 standard interface bus is employed for the hardware compatibility of the communication between the system controller and spectrophotometer subsystems. The Tiny BASIC language is modified as a standard language in the system for real time execution along the communication through the IEEE-488 interface bus. The operation includes two modes: the local mode and the remote mode. In the local mode, the spectrophotometer is manually controlled independently from the system controller. In the remote mode, the modified Tiny BASIC program controls individua...

Research paper thumbnail of A Simple and Versatile Microspectrophotometric System

Applied Spectroscopy, 1979

An easy-to-construct, cost-effective, and versatile microspectrometric system, employing a circul... more An easy-to-construct, cost-effective, and versatile microspectrometric system, employing a circular variable filter as a continuous wavelength scan monochromator, is presented. This simple system includes a single microscope optics, a single photodetector, and a spinning glass plate in conjunction with signal processing electronics, which allows a variety of microspectrometric operations at the cellular level. Three modes of operation, such as double-beam, double-beam derivative, and single-beam wavelength modulated derivative, are provided by minor rearrangements of the optics and the electronic modules. Some spectra of living cells are also presented to demonstrate the system performance.

Research paper thumbnail of Versatile and High-Repetition Subnanosecond Light Source for Fluorescence Lifetime Measurements

Applied Spectroscopy, 1992

We describe the construction and emission characteristics of a gap-adjustable, capacitor-replacea... more We describe the construction and emission characteristics of a gap-adjustable, capacitor-replaceable pulsed light source (air-discharge type) that produces high-repetition pulsed UV light of nanosecond duration. Stable light pulses of 0.8 to 3.5 ns width are generated from atmospheric-pressure air discharge between the sharp anode and round cathode. Appreciable heterogeneities on the distribution of emission intensity and its on-set timing along the discharge gap were observed. Fluorescence lifetimes of ethidium bromide solutions were measured to demonstrate the usefulness of the light source.

Research paper thumbnail of A Photodiode Array Fourier Transform Spectrometer Based on a Birefringent Interferometer

Applied Spectroscopy, 1986

A new version of the photodiode array Fourier transform spectrometer for visible spectroscopy is ... more A new version of the photodiode array Fourier transform spectrometer for visible spectroscopy is described. In this version, a birefringent interferometer with a Wollaston prism produces a spatial interferogram of the radiation, which is detected by a linear photodiode array. In addition to the merit of having no mechanical moving parts, this spectrometer has the beneficial advantage of the simple and rugged optical setup and alignment due to its common-path and in-line interferometer formation. These advantages lend this spectrometer to field-use applications. Emission spectra of a low-pressure mercury lamp and a light-emitting diode and an absorption spectrum of a didymium glass filter measured by the developed spectrometer are presented.

Research paper thumbnail of Fluorescence Pattern Analysis Based on the Time-Resolved Ratio Method

Applied Spectroscopy, 1991

A new technique is described for component pattern analysis based on time-resolved fluorescence i... more A new technique is described for component pattern analysis based on time-resolved fluorescence image detection and a ratio method calculation. Differences in fluorescence lifetimes of components are positively utilized to estimate the spatial distribution of each component. Simulation results of the ratio method for fluorescence pattern analysis are discussed. Spatial deconvolution of multicomponent fluorescence data is rapidly carried out from a set of time-resolved, two-dimensional fluorescence data. An example of the application of a multigate time-resolved ratio method for fluorescence pattern analysis is provided. From the results, it is shown that the new method can be successfully used for multicomponent fluorescence pattern analysis at a reasonable signal-to-noise ratio.

Research paper thumbnail of Burst Radio-Frequency Excited Pulsed Hollow-Cathode Lamp

Applied Spectroscopy, 1980

Transient emission characteristics of a hollow-cathode lamp driven by a pulsed current in combina... more Transient emission characteristics of a hollow-cathode lamp driven by a pulsed current in combination with a radio-frequency burst signal are described. The radio-frequency field excites electrode vapor that is transiently produced by the initial pulsed current discharge. To evaluate the performance of this radio-frequency injected l& peak line intensity, line width and line stability of Cu atomic and ionic emissions are compared to those from dc and pulsed current lamps. Results indicate that the radio-frequency lamp is superior to the conventional pulsed lamp in these three factors. However, due to experimental limitations of commercial lamps under applied radio-frequency voltage, the maximum possible intensity enhancement was not achieved. Atomic absorption working curves are also compared to anticipate practical situations. The steep and linear curve obtained using the radio-frequency lamp suggests its important role in practical analysis.

Research paper thumbnail of Time-Resolved Fluorescence Microscopy Using Multichannel Photon Counting

Applied Spectroscopy, 1990

A new measurement system is reported which combines fluorescence microscopy with multichannel pho... more A new measurement system is reported which combines fluorescence microscopy with multichannel photon-counting detection. The prototype instrument can be operated in normal fluorescence and in fluorescence lifetime modes. Multichannel photon detection was used in order to enhance the rate of data collection. The feasibility of rapid two-dimensional mapping of samples was indicated. The technique may prove especially valuable in situations where multicomponent samples display similar spectral features but differing lifetime characteristics. By increases in the measurement dimensionality, enhanced sample evaluation is possible. Applications involving model and practical biological systems are discussed.

Research paper thumbnail of Application of the Modified UVE-PLS Method for a Mid-Infrared Absorption Spectral Data Set of Water—Ethanol Mixtures

Applied Spectroscopy, 2000

The UVE-PLS (uninform ative variable elimination/ partial least-squares) m ethod 1 originally dev... more The UVE-PLS (uninform ative variable elimination/ partial least-squares) m ethod 1 originally developed by Centner et al. aims at making a better calibration m odel and the resultant high predictive ability in the PLS m ethod. Independent wavelength (or wavenumber) variables that cannot signi® cantly contribute to the model are eliminated, while useful ones are retained. Centner et al. referred to the eliminated variables as uninformative variables. The essence of the UVE-PLS m ethod is addition of noise variables. A set of arti® cial noise variables, the num ber of which is the same as the original experimental (wavelength) ones, are added to the data m atrix as independent variables. Then, som e of the experimental variables that cannot contribute m ore to the model construction than the noise variables are eliminated by a criterion described later. Concerning the procedure of the UVE, most of the conventional and current approaches are to pick up the best wavelength subsets by evaluating the PLS weighting vector or the PLS b-coef® cients, 2±5 the PLS predictive power, 6 and the PLS calibration slopes. 7 Search-based selection methods, such as the genetic algorithm, 8 simulated annealing, 9 arti® cial neural networks, 10 and branch-andbound, 11 have been also developed and studied. Although all those methods m ust work quite well theoretically, it seems that the quality or the degree of contribution of

Research paper thumbnail of Superresolution of Fourier transform spectroscopy data by the maximum entropy method

Research paper thumbnail of Image amplification with local addressing by two-wave coupling in a Bi_12SiO_20 crystal by application of direct-current voltage

Journal of the Optical Society of America B, 1990

We present a proposal and an analysis of local image amplification by two-wave coupling in a Bi12... more We present a proposal and an analysis of local image amplification by two-wave coupling in a Bi12SiO20 crystal by applying external dc voltage. The analogy of two-wave coupling to an optical transistor array is discussed. It is found through the experiments that the local gain in amplification is given not by the reference-beam pattern alone but also by the electric field that is formed by the local photoconductance of the Bi12SiO20 crystal. A resistance-network model is used for analysis of the electric-field distribution. A variety of experiments verify the theoretical and calculated analyses. A sample reference pattern for amplifying segments of a signal image is designed through the resistance-network analysis of the electric-field distribution.

Research paper thumbnail of A Dual Wavelength Atomic Absorption Spectrophotometer Using a Pulsed Hollow Cathode Lamp

Applied Spectroscopy, 1977

A novel use of pulsed hollow cathode lamps for the purpose of background correction with a dual w... more A novel use of pulsed hollow cathode lamps for the purpose of background correction with a dual wavelength atomic absorption spectrophotometer is described. The pulsed hollow cathode lamp in conjunction with a transient signal gating system behaves as if the analyte source and the background correction source are firing alternately in time. Determinations of Fe, Mg, and Cd are carried out in order to evaluate the performance in practical analyses. Procedures and results on the time-resolved measurement of emission spectra and resonance line profiles from several kinds of pulsed hollow cathode lamps are also demonstrated in detail.

Research paper thumbnail of An Optical Null Double-Beam Double-Pass Infrared Spectrophotometer

Applied Optics, 1963

A novel signal treatment for an optical null double-beam double-pass system is developed and used... more A novel signal treatment for an optical null double-beam double-pass system is developed and used in a vacuum-type prism infrared spectrophotometer. A feature of this instrument is the arrangement of the specially-shaped beam switch and the second chopper working in conjunction with the phase-sensitive rectifier. The beam switch is made so that the lower half of the reference beam and the upper half of the sample beam are sent to the monochromator optics during one half of the cycle; the other parts of reference and sample beams reach the monochromator optics during the other half of the cycle. The second chopper alternately blocks the upper and lower halves of the image formed at the focal point of single-pass beam in proper synchronism with the beam switch. Fairly good cancellation of the scattered radiation was achieved through adjustment of the phase relation between the beam choppers and the phase-sensitive rectification system. In addition to reporting the general design and construction, detailed descriptions of the control and recording systems which provide the unique features are also included.

Research paper thumbnail of Three-dimensional phase contrast imaging by an annular illumination microscope

Applied Optics, 1990

A method of observing 3-D phase structures through a microscope incorporating computer reconstruc... more A method of observing 3-D phase structures through a microscope incorporating computer reconstruction is discussed. This microscope is equipped with an annular pupil in illumination optics, but no phase shifter is included in the imaging optics. The sample stage is longitudinally (z-axial) scanned to collect a focus image series. The 3-D phase transfer function is derived and computer-plotted based on Streibl's 3-D image transfer theory under the first-order Born approximation and the mutual intensity propagation theorem. Experimental results of 3-D phase reconstruction are shown with cultured tobacco cells by Helstrom's inverse filtering of the transfer function to a series of focused images.

Research paper thumbnail of Three-dimensional phase-contrast imaging by a computed-tomography microscope

Applied Optics, 1992

We report a technique for measuring the three-dimensional variation of refractive indices in a mi... more We report a technique for measuring the three-dimensional variation of refractive indices in a microscopic sample. The technique is an adaptation of optical computed tomography and is effective in measuring the three-dimensional refractive-index distribution of a nonabsorbing microscopic sample. Our report also includes a discussion of the conditions for the unambiguous application of the technique as well as results of experiments conducted with Aspergillus oryzae (commonly known as green mold) as the sample.

Research paper thumbnail of Application of Optical Multichannel Dectors to Spectroscopic Measurement

Journal of the Spectroscopical Society of Japan, 1991

Research paper thumbnail of Evaluation of Numerical Filters for Smoothing Spectroscopic Data

Japanese Journal of Applied Physics, 1969

In recent years, numerical filtering is often used for the smoothing of spectroscopic data. This ... more In recent years, numerical filtering is often used for the smoothing of spectroscopic data. This article is concerned with the computer analysis of numerical filters to find their optimal setup for spectroscopic measurements. Gaussian and Lorentzian contours are assumed for shapes of input signals to the filter in consideration of spectroscopic measurements. The distortion of the signal waveforms and the output noise levels are computed for the input data contaminated with the white or correlated noise. From the computed results which are summalized in the graphical presentation, optimal operating parameters of the data source and the succeeding filtering system are easily determined.

Research paper thumbnail of A Simple Photomultiplier Gating Circuit for the Nanosecond Region

Japanese Journal of Applied Physics, 1976

A novel nanosecond photomultiplier gating circuit is developed and applied to three kinds of phot... more A novel nanosecond photomultiplier gating circuit is developed and applied to three kinds of photomultiplier tubes. For the purpose of simply accomplishing accurate gating operation in the nanosecond region, even numbered dynodes which are deeply biased are simultaneously controlled by the delayed pulses which are adjusted in time so as to synchronize with traveling electrons in the tube. To evaluate

Research paper thumbnail of Corrected Performance of SIT Vidicons Exposed to Transient Radiation

Applied Spectroscopy, 1990

ABSTRACT The SIT vidicon detector has many features which would indicate utility as a detector fo... more ABSTRACT The SIT vidicon detector has many features which would indicate utility as a detector for time-resolved spectroscopy. Unfortunately, the problem of capacitive lag, under pulsed detection modes, can lead to highly erroneous spectroscopic intensities and linewidths. We have theoretically modeled the capacitive lag characteristics of the SIT vidicon and have developed a mathematical "correction factor" which can result in greatly enhanced performance. Results will be described for pulsed-LED test sources. Application to a variety of transient discharges appears possible.

Research paper thumbnail of A Nanosecond Photon-Counting Fluorimetric System Using a Modified Multichannel Vernier Chronotron

Applied Spectroscopy, 1985

A new time-resolved photon-counting instrument with high data-gathering efficiency is described. ... more A new time-resolved photon-counting instrument with high data-gathering efficiency is described. The principle of operation is based on the measurement of the nanosecond temporal distribution of the emitted photon burst during the short duration of transient emission. The instrument is characterized by the unique capabilities of a modified vernier chronotron with plural coincidence circuits and serial-timing data memories, which serve as an efficient multichannel event-time analyzer of 1.5-ns time resolution. The data-gathering efficiency is improved by a factor of 20 or more in comparison with that of the conventional single-photon counting method. In regular operation, the time history of transient emission for the period of 144 ns is obtained; and for phenomena with longer duration, the time-scale expansion mode of operation is provided. To demonstrate the whole system performance, a fluorescence decay curve of 1-ppm quinine sulfate in 0.1-N H2SO4 is presented.

Research paper thumbnail of A Pulse-Operated Microwave-Induced Plasma Source

Applied Spectroscopy, 1989

A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational dif... more A new pulse-operated microwave-induced plasma (MIP) source is described. To avoid operational difficulties of the MIP due to Joule heating and to obtain spectral emission lines of high peak intensities, one energizes the MIP source with a TM010 cavity with a microwave pulse of large peak power and short duration, which is superposed on a low-bias dc microwave. A peak power of 400 W, which is two times the maximum output ratings of a magnetron under a normal dc operation, can be generated by applying a −500 V pulse to the cathode of the magnetron operating under the bias mode. The pulsed-MIP requires no special cooling system since the mean power remains low during the entire operation. Some of the considerations taken into account in the design and construction of the microwave generator are presented. The electrical and spectral characteristics of the MIP source are also described in detail.

Research paper thumbnail of A Small Laboratory Automation System Composed of Microcomputer-Based Spectrophotometers

Applied Spectroscopy, 1983

A distributed microcomputer network system which consists of integral microprocessors in intellig... more A distributed microcomputer network system which consists of integral microprocessors in intelligent instruments has been developed for automating the spectroscopy laboratory. In this system, the master-slave arrangement of microcomputers is adopted to compose the system controller and three microcomputer-based spectrophotometers (an UV/visible spectrophotometer, an IR spectrophotometer, and a fluorescence spectrophotometer). The IEEE-488 standard interface bus is employed for the hardware compatibility of the communication between the system controller and spectrophotometer subsystems. The Tiny BASIC language is modified as a standard language in the system for real time execution along the communication through the IEEE-488 interface bus. The operation includes two modes: the local mode and the remote mode. In the local mode, the spectrophotometer is manually controlled independently from the system controller. In the remote mode, the modified Tiny BASIC program controls individua...

Research paper thumbnail of A Simple and Versatile Microspectrophotometric System

Applied Spectroscopy, 1979

An easy-to-construct, cost-effective, and versatile microspectrometric system, employing a circul... more An easy-to-construct, cost-effective, and versatile microspectrometric system, employing a circular variable filter as a continuous wavelength scan monochromator, is presented. This simple system includes a single microscope optics, a single photodetector, and a spinning glass plate in conjunction with signal processing electronics, which allows a variety of microspectrometric operations at the cellular level. Three modes of operation, such as double-beam, double-beam derivative, and single-beam wavelength modulated derivative, are provided by minor rearrangements of the optics and the electronic modules. Some spectra of living cells are also presented to demonstrate the system performance.

Research paper thumbnail of Versatile and High-Repetition Subnanosecond Light Source for Fluorescence Lifetime Measurements

Applied Spectroscopy, 1992

We describe the construction and emission characteristics of a gap-adjustable, capacitor-replacea... more We describe the construction and emission characteristics of a gap-adjustable, capacitor-replaceable pulsed light source (air-discharge type) that produces high-repetition pulsed UV light of nanosecond duration. Stable light pulses of 0.8 to 3.5 ns width are generated from atmospheric-pressure air discharge between the sharp anode and round cathode. Appreciable heterogeneities on the distribution of emission intensity and its on-set timing along the discharge gap were observed. Fluorescence lifetimes of ethidium bromide solutions were measured to demonstrate the usefulness of the light source.

Research paper thumbnail of A Photodiode Array Fourier Transform Spectrometer Based on a Birefringent Interferometer

Applied Spectroscopy, 1986

A new version of the photodiode array Fourier transform spectrometer for visible spectroscopy is ... more A new version of the photodiode array Fourier transform spectrometer for visible spectroscopy is described. In this version, a birefringent interferometer with a Wollaston prism produces a spatial interferogram of the radiation, which is detected by a linear photodiode array. In addition to the merit of having no mechanical moving parts, this spectrometer has the beneficial advantage of the simple and rugged optical setup and alignment due to its common-path and in-line interferometer formation. These advantages lend this spectrometer to field-use applications. Emission spectra of a low-pressure mercury lamp and a light-emitting diode and an absorption spectrum of a didymium glass filter measured by the developed spectrometer are presented.

Research paper thumbnail of Fluorescence Pattern Analysis Based on the Time-Resolved Ratio Method

Applied Spectroscopy, 1991

A new technique is described for component pattern analysis based on time-resolved fluorescence i... more A new technique is described for component pattern analysis based on time-resolved fluorescence image detection and a ratio method calculation. Differences in fluorescence lifetimes of components are positively utilized to estimate the spatial distribution of each component. Simulation results of the ratio method for fluorescence pattern analysis are discussed. Spatial deconvolution of multicomponent fluorescence data is rapidly carried out from a set of time-resolved, two-dimensional fluorescence data. An example of the application of a multigate time-resolved ratio method for fluorescence pattern analysis is provided. From the results, it is shown that the new method can be successfully used for multicomponent fluorescence pattern analysis at a reasonable signal-to-noise ratio.

Research paper thumbnail of Burst Radio-Frequency Excited Pulsed Hollow-Cathode Lamp

Applied Spectroscopy, 1980

Transient emission characteristics of a hollow-cathode lamp driven by a pulsed current in combina... more Transient emission characteristics of a hollow-cathode lamp driven by a pulsed current in combination with a radio-frequency burst signal are described. The radio-frequency field excites electrode vapor that is transiently produced by the initial pulsed current discharge. To evaluate the performance of this radio-frequency injected l& peak line intensity, line width and line stability of Cu atomic and ionic emissions are compared to those from dc and pulsed current lamps. Results indicate that the radio-frequency lamp is superior to the conventional pulsed lamp in these three factors. However, due to experimental limitations of commercial lamps under applied radio-frequency voltage, the maximum possible intensity enhancement was not achieved. Atomic absorption working curves are also compared to anticipate practical situations. The steep and linear curve obtained using the radio-frequency lamp suggests its important role in practical analysis.

Research paper thumbnail of Time-Resolved Fluorescence Microscopy Using Multichannel Photon Counting

Applied Spectroscopy, 1990

A new measurement system is reported which combines fluorescence microscopy with multichannel pho... more A new measurement system is reported which combines fluorescence microscopy with multichannel photon-counting detection. The prototype instrument can be operated in normal fluorescence and in fluorescence lifetime modes. Multichannel photon detection was used in order to enhance the rate of data collection. The feasibility of rapid two-dimensional mapping of samples was indicated. The technique may prove especially valuable in situations where multicomponent samples display similar spectral features but differing lifetime characteristics. By increases in the measurement dimensionality, enhanced sample evaluation is possible. Applications involving model and practical biological systems are discussed.

Research paper thumbnail of Application of the Modified UVE-PLS Method for a Mid-Infrared Absorption Spectral Data Set of Water—Ethanol Mixtures

Applied Spectroscopy, 2000

The UVE-PLS (uninform ative variable elimination/ partial least-squares) m ethod 1 originally dev... more The UVE-PLS (uninform ative variable elimination/ partial least-squares) m ethod 1 originally developed by Centner et al. aims at making a better calibration m odel and the resultant high predictive ability in the PLS m ethod. Independent wavelength (or wavenumber) variables that cannot signi® cantly contribute to the model are eliminated, while useful ones are retained. Centner et al. referred to the eliminated variables as uninformative variables. The essence of the UVE-PLS m ethod is addition of noise variables. A set of arti® cial noise variables, the num ber of which is the same as the original experimental (wavelength) ones, are added to the data m atrix as independent variables. Then, som e of the experimental variables that cannot contribute m ore to the model construction than the noise variables are eliminated by a criterion described later. Concerning the procedure of the UVE, most of the conventional and current approaches are to pick up the best wavelength subsets by evaluating the PLS weighting vector or the PLS b-coef® cients, 2±5 the PLS predictive power, 6 and the PLS calibration slopes. 7 Search-based selection methods, such as the genetic algorithm, 8 simulated annealing, 9 arti® cial neural networks, 10 and branch-andbound, 11 have been also developed and studied. Although all those methods m ust work quite well theoretically, it seems that the quality or the degree of contribution of

Research paper thumbnail of Superresolution of Fourier transform spectroscopy data by the maximum entropy method